The invention relates to an electron beam vaporizer consisting of a beam generator with a heatable cathode, focusing means, and electromagnetic deflection means for the deflection and guidance of the beam, and a replaceable, liquid-cooled and preferably rotatable vaporizing crucible which is associated with the beam generator, has at least one cavity for at least one substance to be vaporized, and has passages in the base of the crucible underneath the said cavity or cavities to carry the circulating coolant.
In electron beam vaporizers it is often necessary to adapt the vaporizing crucible to a particular vaporizing task and in this case to replace it, even at short intervals of time; with vaporizing crucibles of different geometrical configuration, e.g., with a different arrangement of the cavities. Shallow vaporizing crucibles of great breadth are required, successively as a rule, for the accommodation of comparatively large amounts of material in powder form, in a single cavity of large area. For other purposes, such as the formation of alloy coatings and/or interference systems in the field of optics, crucibles are often required which have several cavities for the accommodation of different vaporizing materials. The cavities in this case can be truncoconical depressions in the crucible surface, which are distributed more or less uniformly over its circumference. The individual vaporizing substances are then brought into the path of the electron beam by periodical rotation of the vaporizing crucible and/or by changes in the deflection of the beam. It is also possible, for example, to provide the vaporizing crucibles with a plurality of concentric, annular grooves to receive different vaporizing substances, and to sweep these grooves alternately, for example, with a jumping electron beam, while at the same time a rotation of the vaporizing crucible is performed so as to bring always fresh material into the path of the beam. In the case of the vaporizing of a plurality of substances it will, of course, be necessary to assure that the vapor depositing system is not vented between the vaporizing of the individual components. As a rule, therefore, a plurality of crucible arrangements must be held ready for the electron beam vaporizer.
It can also come about that, due to errors of beam positioning and/or to thermal overstressing of the crucible--if the crucible should run out of the material being vaporized for example--the crucible may become damaged and have to be replaced.
For the purpose outlined above, it is known to mount the vaporizing crucible with the cooling channels releasably on a base frame by means of a flange, with the interposition of a gasket, the base frame containing the cooling input and output lines (German "Offenlegungsschrift" No. 2,206,995, p. 10, last paragraph, and p. 11, par. 1). The design of the crucible in this case, however, is complex, since each crucible must be equipped with complete cooling passages, and also it necessitates, in the case of rotatable crucibles, a vacuum-tight seal between the rotatable part and the stationary part. This complex construction must be provided in each and every one of the interchangeable crucibles. Such a crucible is furthermore hard to clean, and this is very important in view of the high purity which is usually required in coatings deposited from vapors. Also, the set-up work that has to be done when the crucible is replaced is difficult, and the entire electron beam vaporizer has to be disassembled for this purpose, since in this case the system of coolant passages is opened up. Disassembly within the vacuum chamber is difficult, complicated and time-consuming, and while the vacuum is applied it is, of course, utterly impossible.
It is also known to replace only the rotatable part of the crucible, disconnecting it from the stationary part. In this system, too, the coolant passage network is opened up; also, such a crucible is of complex shape, so that here again the replacement of the crucible can be accomplished only through the complete disassembly of the electron beam vaporizer.